The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-250mm F3.5-6.3 DC OS HSM and the Nikon 18-140mm f3.5-5.6G ED VR for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Nikon 18-140mm f3.5-5.6G ED VR is the longer of the two lenses at 97mm. The Sigma 18-250mm F3.5-6.3 DC OS HSM with a length of 89mm, is 8mm shorter. Besides being longer, the Nikon 18-140mm f3.5-5.6G ED VR also has a larger diameter of 78mm compared to the Sigma 18-250mm F3.5-6.3 DC OS HSM's 74mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Sigma 18-250mm F3.5-6.3 DC OS HSM weighs 470g, which means it is 20g (4%) lighter than the Nikon 18-140mm f3.5-5.6G ED VR which has a weight of 490g.
Filter Threads
The Sigma 18-250mm F3.5-6.3 DC OS HSM has a filter size of 72mm whereas the Nikon 18-140mm f3.5-5.6G ED VR has a 67mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 72mm filters that we recommend you to consider for the Sigma 18-250mm F3.5-6.3 DC OS HSM:
And these are the 67mm filters that we recommend for the Nikon 18-140mm f3.5-5.6G ED VR:
Lens Mounts
Both the Sigma 18-250mm F3.5-6.3 DC OS HSM and the Nikon 18-140mm f3.5-5.6G ED VR has the same Nikon F (DX) lens mount. Some of the latest released cameras that are compatible with the Nikon F (DX) lenses are Nikon D3500, Nikon D7500 and Nikon D5600.
Sigma 18-250mm F3.5-6.3 DC OS HSM is also available in Canon EF , Pentax KAF3, Sony Alpha, Sigma SA, Canon EF, Nikon F (DX), Pentax KAF3, Sony Alpha and Sigma SA mounts.
Focal Range
Sigma 18-250mm F3.5-6.3 DC OS HSM has a focal range of 18-250mm and
13.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-375mm when used on a APS-C / DX format camera.
On the other hand, the Nikon 18-140mm f3.5-5.6G ED VR has a focal range of 18-140mm and 7.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-210mm when used on a APS-C / DX format camera.